This invention relates to an automatic document feeder of a copier and the like and more particularly to an automatic document feeder in which documents stacked on a document tray are conveyed onto a platen glass one sheet by one sheet and delivered out to a document delivery unit after exposure.
In a conventional automatic document feeder, a document delivery out means such as a document delivery roller is driven by the drive force transmitted from a document feed conveyance means located on a platen glass in such a manner that: the document delivery out means and the document feed conveyance means are connected by a timing belt so that the delivery out means can be driven by the conveyance means. In the case of the document feeder described above, the document feed conveyance means on the platen glass needs to be driven until the document is delivered out from the document delivery means. As a result, it has such disadvantages that: the consumption of electric power is increased, so that the document feed conveyance means on the platen glass and the like are worn out fast, and furthermore the interval between the document delivered out from on the platen glass and the following document conveyed onto the platen glass needs to be kept longer than the distance between the conveyance means and the delivery out means. For that reason, there is a problem that it takes a long period of time to replace a document at an exposure position, so that the processing speed of the document feeder is decreased.
The object of the present invention is to solve the problems described above. The first object of the present invention is to provide an automatic document feeder which is characterized in that: the document feed conveyance means on the platen glass can be stopped before the document is delivered out by the delivery means; the interval between the document to be delivered out and the document to be fed for replacing the document at the exposure position, can be made shorter than the distance between the conveyance means and the delivery out means; the consumption of electric power can be reduced and the conveyance means and the like are less worn out; and further the total document processing time can be reduced.
In the conventional automatic document feeder described above, document feed is conducted in such a manner that: the conveyance means located on the platen glass further conveys the document which has been fed by a document feed means until the leading edge of the document comes into contact with the stopper at the end of the platen glass so that the document can be positioned on the platen glass; and when the document is delivered out from the platen glass to the delivery conveyance means, the document is conveyed passing through the platen glass, so that the document conveyance direction by the document feed conveyance means located on the platen glass is one way. For the reason explained above, there is a problem in the conventional automatic document feeder, that when the document on the platen glass is delivered out, the stopper at the end of the platen glass needs to be withdrawn so that the stopper does not obstruct document conveyance.
In order to solve the problem described above, the second object of the present invention is to provide an automatic document feeder which is characterized in that: when the document located on the platen glass is delivered out, it is not necessary to withdraw the stopper at the exposure position.